The present invention relates generally to flotation sleep systems and, more particularly, to a heated waterbed having a plurality of water-filled receptacles or tubes as a mattress and a heating unit to heat the mattress.
It is usually desirable to use a heating unit in a waterbed construction to provide a heated flotation sleep system upon which the individual lies or sleeps. In the absence of a heating unit, the water-filled waterbed mattress remains cold and uncomfortable to the individual, especially during the winter months.
Likewise, it is usually preferable to construct a flotation sleep system so that the waterbed mattress is composed of a plurality of individual water-filled units, as opposed to one large water-filled mattress. Such a plurality of water-filled units provides a smoother, less oscillating mattress surface than one large water-filled mattress. Moreover, the use of a number of smaller, individual water-filled units prevents excessive damage to the surrounding room from a leak and makes it easier to fill and transport the waterbed.
However, it previously has not been possible to use effectively in the same waterbed construction both a heating unit and a plurality of water-filled units, without causing numerous safety hazards. The plurality of water-filled units have a propensity to form a number of air gaps. When an air gap is contacted by the heating unit, the air within the air gap is heated to a temperature in excess of a safe maximum temperature. Such an overheating of the air in the air gap causes damage to the waterbed, as well as posing a safety and fire hazard.
The problem of air gap overheating due to contact with the heating unit has developed as a result of the nature and construction of waterbed heater pads, as presently available in the waterbed industry. Basically, all waterbed heater pads are composed of resistance electrical circuits. Such resistance circuits are generally constructed of either etched metal, wire, or a carbon particle mat. In all cases, regardless of the material used, an electric current is passed through the conductive material that creates a certain degree of resistance to the passage of the current. This resistance causes the material to generate heat.
The resistance circuit is usually encased in an insulating polymeric material, such as vinyl or rubber. The flow of the electric current to the heater pad is typically regulated by means of a controller, which turns the power on and off based upon the setting made and the water temperature, as measured by a thermostat probe. One type of controller, however, also turns the current on and off based upon a thermostatic setting that measures and responds to the ambient room temperature.
Underwriter's Laboratories (U.L.) standards require that the electrical connection to the heater pad, located in a housing on the top side of the pad, contains a fixed thermostat, which is known in the industry as a safety-override thermostat. The purpose of the safety-override thermostat is to break the flow of electric current to the heater circuit of the heater pad, if the water temperature surrounding the safety-override thermostat reaches between 135.degree. and 145.degree. F.
If an air gap occurs between the heater pad surface and the bottom of the waterbed mattress, an insulation effect can take place in the area around the air gap. Since the position of this insulation effect prevents the heater pad, in contact with the air gap, to dissipate its heat, as a result the air gap builds up heat and eventually reaches a temperature that will melt or burn the polymeric insulation materials of the heater pad and any other adjacent materials.
If such an air gap occurs in the area directly around the safety-override thermostat, the safety-override thermostat alleviates the problem of heat build up by breaking the current flow to the heater pad. However, the area around the thermostat is only a few square inches and, hence, the likelihood of an air gap occurring in another area of the heater pad is significant. When the air gap forms in an area away from the thermostat, the safety-override thermostat continues to sense a water temperature below the minimum temperature needed to activate the safety cut-off, such as 135.degree. F.
Consequently, in most cases, the safety-override thermostat provides no protection against burn-outs caused by the overheating of the air gaps. Heater pad manufacturers call attention to this danger, by warning that the area directly over the heater pad should be free of any wrinkles and air gaps when a waterbed liner and mattress are installed.
When a single heater pad is placed directly in contact with a dual waterbed mattress or a waterbed mattress composed of a plurality of water-filled containers, the air gap overheating problem, previously described, can occur with a greatly increased frequency. This is due to the fact that there is a tendency for air gaps to occur in-between the dual waterbed mattresses and water-filled containers, as they are installed in a side by side manner within the waterbed construction.
The problem of air gap overheating has previously rendered the heating of dual waterbed matresses or multiple container waterbed mattress systems very ill advised. As a result of the air gap overheating problem, multiple container waterbed mattress systems have not been able to be heated safely and, therefore, the users of the waterbed are denied one of the major benefits of a flotation sleep system, namely, heat.